Hydroformed space frame and method of manufacturing the same

ABSTRACT

A space frame includes a pair of laterally spaced, longitudinally extending side rail structures and longitudinally spaced pairs of laterally spaced upright structures having joints at their lower ends with the pair of side rail structures. The longitudinal spaced pairs of laterally spaced upright structures extend upwardly from the side rails structures and define a plurality of pairs of pillars, including a pair of forward A pillars, a longitudinally spaced pair of B pillars, and a longitudinally spaced pair of rearward end pillars. A pair of the side roof structures has joints with the pair of A pillars. The pair of side roof structures extends longitudinally rearwardly from the pair of A pillars and have joints with the pair of B pillars and with the pair of rearward end pillars. Longitudinally spaced cross structures have joints with the pair of side rail structures, with the pair of A pillars and with the pair of side roof structures. A front structural assembly has joints with a forward end of the pair of side rail structures and with the A pillars at positions spaced upwardly of the pair of side rail structures. A plurality of the structures have more than two spaced successive joints which determine defining lengths in the space frame. The plurality of structures comprise a pair of hydroformed tubular members, each of which is defined by an irregularly outwardly deformed tubular metallic wall fixed into a predetermined irregular exterior surface configuration.

This is a division of application Ser. No., 09/173,554, filed Oct. 16,1998, now U.S. Pat. No. 6,092,865 and also claims the benefit ofpriority from Provisional application No. 60/062,204. filed Oct. 16,1997.

FIELD OF THE INVENTION

The present invention relates to space frames for motor vehicles.

BACKGROUND OF THE INVENTION

It is known in the automotive industry to provide a vehicle space framewhich can be used to mount various components and body panels for themotor vehicle. Typically, the space frame is made from many framestructures which are joined together by welding or other types ofconnections. The numerous connections that are typically required toform a space frame from the frame structures leads to tolerancebuild-up, which causes dimensional accuracy problems in the space frame.

It is an object of the invention to provide a space frame that requiresfewer parts and fewer connections than the conventional space frame, sothat a space frame of greater dimensional accuracy can be produced.

In accordance with this object, the present invention provides a spaceframe for a motor vehicle, comprising a first hydroformed,longitudinally extending tubular lower side rail member, and a secondhydroformed, longitudinally extending tubular lower side rail member,the lower side rail members being laterally spaced from one another.Also included is a pair of hydroformed tubular upper longitudinalmembers, each being an integrally formed member fixed to an associatedone of the lower side rail members. The structure of each upperlongitudinal member includes a longitudinally extending portionconstructed and arranged to support a roof of the motor vehicle, eachlongitudinally extending portion extending longitudinally between anupper end of an A-pillar structure provided by the space frame and anupper end of a rearward-most pillar structure of the space frame. Thehydroformed tubular upper longitudinal members thus define lengthsbetween the vehicle A-pillar structures and the rearward-most structuresof the space frame. Laterally extending connecting structure connectsthe lower side rail members to one another.

The object of the present invention can be achieved by other structuralcomponents, as well as various method of manufacture. For example, inone method of the invention, the following steps are performed: placinga tubular metal blank having a generally U-shaped configuration into ahydroforming die assembly, the die assembly having die surfaces defininga die cavity; providing pressurized fluid to an interior of the tubularmetal blank so as to expand the blank into conformity with the diesurfaces of the die cavity and thereby form a U-shaped hydroformed crossmember; positioning first and second lower side rail members inlaterally spaced relation to one another; connecting a first end of thehydroformed cross member to the first lower side rail member; andconnecting a second end of the hydroformed cross member to the secondlower side rail member.

Because fewer parts are required in accordance with the space frame ofthe present invention, assembly is made much simpler.

SUMMARY OF THE INVENTION

An object of the present invention is to meet the need expressed aboveby providing a space frame comprising a pair of laterally spaced,longitudinally extending side rail structures and longitudinally spacedpairs of corresponding laterally spaced upright structures having jointsat their lower ends with the pair of side rail structures and extendingupwardly therefrom defining a plurality of pairs of pillars including apair of forward A pillars, a longitudinally spaced pair of B pillars,and a longitudinally spaced pair of rearward end pillars. A pair of theside roof structures are integral with the pair of A pillars. The pairof side roof structures extend longitudinally rearwardly from the pairof A pillars and the pair of side roof structures have joints with thepair of B pillars and the pair of rearward end pillars. Longitudinallyspaced cross structures have joints with the pair of side railstructures, the pair of A pillars and the pair of side roof structures.A front structural assembly has joints with a forward end of the pair ofside rail structures and with the A pillars at positions spaced upwardlyof the pair of side rail structures. A plurality of all of thestructures are hydroformed members, each hydroformed member beingdefined by an irregularly, outwardly deformed tubular metallic wallfixed into a predetermined irregular exterior surface configuration. Thehydroformed members include a pair of hydroformed members forming thepair of side roof structures integral with the A pillars and having morethan two spaced successive joints which determine defining longitudinallengths in the space frame.

Other objects, features, and advantages of the present invention willbecome apparent from the following detailed description, theaccompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vehicle space frame manufactured inaccordance with the principles of the present invention;

FIG. 2 is a perspective view of a connection between a rearwardcross-structure at one corner portion thereof and the associateduppermost straight portion of one of the longitudinal upper structuresof the first embodiment illustrated in FIG. 1,

FIGS. 3 and 4 are a cross-sectional view and a partial perspective viewof the straight portion of the connection illustrated in FIG. 2;

FIG. 5 is a perspective view of a second embodiment of a vehicle spaceframe manufactured in accordance with the principles of the presentinvention;

FIGS. 6-11 are perspective views of various stages of assembly of spaceframe illustrated in FIG. 5;

FIGS. 12-47 are various enlarged views of Joints A-T illustrated inFIGS. 6-11; and

FIG. 48 is a cross-sectional view of a hydroforming die assembly forillustrating the method in accordance with the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of a vehicle space frame 10 manufactured inaccordance with the principles of the present invention. The vehiclespace frame 10 comprises a pair of laterally spaced, longitudinallyextending lower side structures 11. Each of the side structures 11 has arelatively straight forward portion 14 which transitions into anupwardly and rearwardly sloping intermediate portion 16. In addition,each of the side structures 11 includes a generally straight rearwardportion 18 extending rearwardly from the upper rearward end of theintermediate portion 16. The forward portion 14 and rearward portion 18of the lower side rail structures 11 are disposed generallyhorizontally, and parallel to the ground and one another in an assembledvehicle. The intermediate portion 16 provides the rear “kick-up” foraccommodating a rear wheel well.

The side rail structures 11 are preferably each formed from a straighttubular blank (formed by conventional roll forming and seam welding)which are bent generally into the “S” configuration shown, thendiametrically expanded, and shaped in any conventional hydroformingoperation to form two hydroformed lower side rail members 12.

The vehicle space frame 10 further includes a pair of longitudinal upperstructures 19 having a generally inverted U-shaped configuration. Eachupper structure 19 is preferably a hydroformed member 20, referred to asan upper member or a longitudinal upper member. Each of the uppermembers 20 includes a forwardly disposed, lower vertical portion 22,which transitions into an upwardly and rearwardly extending forwardportion 24. The portions 22 and 24 form the “A-pillar” structures of thevehicle space frame, as generally indicated at 25. Each longitudinalupper member 20 further includes an uppermost, longitudinally extending,generally straight portion 26, or also referred to as a straight portionwhich transitions from and extends rearwardly from the upwardly andrearwardly extending forward portions 24. The straight portions 26constitute the bight portion of the generally inverted U-shapedconfiguration of the longitudinal upper member 20 and provides roofstructure for the space frame 10. Towards the rearward portion of thelongitudinal upper members 20 are downwardly and rearwardly extendingportions 28, which transition from the rearward portions of theuppermost straight portions 26. The downwardly and slightly rearwardlyextending portions 28 form the space frame “D-pillar” structures.Finally, the longitudinal upper members 20 each terminate in respectivelower end portions 30 connected with the rearward ends of side railmembers 12.

As shown, each longitudinal upper member 20 preferably has a generallyrectangular, closed cross-section throughout its extent. In addition, itshould be appreciated that both of the longitudinal upper members 20have been hydroformed from a single tubular blank structure, preferablyformed from two separately roll-formed tubular members which have beenbutt-welded to one another at butt-welded connection 32. In particular,the butt-welded connection 32 is performed prior to the hydroformingoperation and connects two separate tubular blank members of differentdiameter to one another. More specifically, because the lower verticalportions 22 have a much greater diameter than the upwardly andrearwardly extending forward portions 24, these portions of eachlongitudinal upper member 20 are preferably formed from blanks havingsubstantially different diameters. The connection 32 can be accomplishedby either utilizing a reduction tool for reducing a diameter of one endof the tubular blank which eventually forms the lower vertical portion22 so that such end of the blank can be butt-welded to the end of thesmaller diameter roll-formed blank which eventually forms the rest ofthe longitudinal upper member, referred to as upper and rear portion 33.The upper and rear portion 33 constitutes the upwardly and rearwardlyextending forward portion 24, the straight portion 26, the downwardlyand rearwardly extending portion 28, and the lower end portion 30.Alternately, a flaring or expansion tool can be used to expand thesmaller diameter blank at the end thereof which is to form the lowerforward end of the upwardly and rearwardly extensions forward portion 24so as to provide the end of that blank portion (which forms portion 33)with substantially the same diameter as the adjoining end of the blankwhich is to form the lower vertical portion 22. The butt-weldingoperation can be performed either before or after the relevant tubularblank portions (which are to form portion 33) are bent into a U-shapedconfiguration. Bending of the blank is conducted prior to hydroforming.After the blank portions are butt welded to one another to form acomplete single blank structure, the single blank structure ishydroformed as a single structure into the associated longitudinal uppermember 20.

In view of the rather severe bends of >30° in the U-shaped longitudinalupper structures 20 and in the side rails 12, the present inventionpreferably employs the teachings of U.S. Ser. No. 60/061,238, filed Oct.7, 1997, entitled METHOD AND APPARATUS FOR WRINKLE-FREE HYDROFORMING OFANGLED TUBULAR PARTS, and hereby incorporated by reference, to avoidwrinkle formation at the concave portion of the bends.

As shown, the lower side rail members 12 have a varying cross-sectionalconfiguration along its longitudinal extent. For example, towards therearward portion 18, the lower side rail members 12 preferably have asubstantially rectangular cross-section. Towards the more forwardportions 14, the lower side rail members 12 have a substantiallyhexagonal cross-sectional configuration. Altering the cross-sectionalconfiguration of this member or other tubular hydroformed membersdisclosed herein can be accomplished without departure from theprinciples of the present invention.

As shown, the lower edge 34 of each of the lower vertical portions 22 iscontoured to form-fittingly receive the corresponding upper surfaceportions 35 of the forward portion 14 of the lower side rail members 12.The lower edges 34 are cut into such form-fitting configuration afterthe hydroforming operation is completed. After the edges 34 arepositioned on upper surface portions 35, they are preferably mig-weldedin place.

In similar fashion, the rearward portions 18 of the lower side rails 12terminate in cut-out edges 36. The edges 36 are each constructed andarranged to receive a corner portion of the lower end portion 30 of theassociated upper longitudinal structure 20. More specifically, the lowerend portions 30 each have a rectangular cross-section. The edges 36 ofthe lower side rail members 12 are formed as cut-outs so as to engagethe outboard facing surface 38 and the forwardly facing surface 40 ofthe lower end portion 30. The edge 36 is preferably mig-welded to thelower end portion 30.

A plurality of cross-structures are interconnected between thelongitudinal upper members 20. In particular, a first cross-structure 43comprises a hydroformed tubular first cross member 44 having asubstantially rectangular cross-section and connected between thelongitudinal upper members 20, preferably towards the lower portions ofthe upwardly and rearwardly extending forward portions 24 andimmediately above the butt-welded connections 32. Similarly, across-structure provided by a hydroformed cross-member 46 connects thetwo longitudinal upper members 20, generally at the bending or arcuatetransition between the upwardly and rearwardly extending forwardportions 24 and the uppermost straight portions 26. In addition, arearward cross-structure provided by a hydroformed cross-member 48extends between the longitudinal upper members 20, generally at thebending or arcuate transition between the uppermost straight portions 26and the downwardly and rearwardly extending portions 28. Preferably,each of these cross-members 44, 46, 48 has a generally rectangularcross-sectional configuration and is hydroformed from a circular tubularblank in conventional fashion.

The cross-members 44,46 and 48 have opposite ends thereof disposed inoverlapping or overlying relation with adjoining portions of uppermembers 20, and are received in recesses which are hydroformed into theexterior configuration of longitudinal upper members 20 and mig-weldedin place. The recesses formed in the longitudinal upper member 20 arepreferably formed in a hydroforming operation, as will be described.

A pair of inverted U-shaped cross-structures 49 and 51 are disposedbetween the cross-members 46 and 48. The cross-structures 49, 51 arepreferably provided by two inverted U-shaped hydroformed cross members50, 52. The forwardly disposed U-shaped hydroformed cross member 50 hasa generally horizontally disposed bight portion 54 extending in across-car direction, and a pair of integral leg portions 56 extendingdownwardly from the opposite ends of the bight portion 54. Comerportions 58 of the cross-member 50 form the transition between the bightportion 54 and the respective leg portions 56. The corner portions 58are disposed in overlying or overlapping relation with adjacent,underlying portions of the uppermost straight portions 26. The bottomedges 60 of the leg portions 56 are cut so as to be form fitting withrespect to the adjacent upper surfaces 35 of the respective lower siderail members 12. The edges 60 are then mig-welded to the upper surface35 of the lower side rail members 12.

The corner portions 58 are received in hydroformed recesses formed inthe exterior configuration of the uppermost straight portions 26, aswill be described later, to form overlapping glove-joints with theassociated uppermost straight portions 26 and mig-welded in place.

The rearward cross-member 52 comprises a bight portion 70, which issubstantially horizontally disposed and extends in the cross-cardirection. The bight portion 70 transitions into vertically downwardlyextending leg portions 72 from the opposite ends of the bight portion70. Corner portions 74 form the transition between the bight portion 70and the respective leg portions 72. The corner portions 74 are disposedin overlapping or overlying relation to adjacent portions of theuppermost straight portions 26. In particular, the corner portions 74are disposed in hydroformed recesses formed in the exteriorconfiguration of the uppermost straight portions 26 as will be describedlater.

The leg portions 72 have ends 76 thereof received within recesses whichare hydroformed in the associated lower side rail members 12 andmig-welded in place. Again, the recess is formed within the lower siderail members 12 for receiving the end portions 76 as will be describedlater.

Again, the teachings of U.S. Ser. No. 60/061,238 are preferably employedto avoid wrinkling at the bends (corner portions 58 and 74) in thecross-members 50 and 52.

It should be appreciated that the legs 56 of cross-member 50 form the“B-pillar” structures of the space frame. Similarly, the legs 72 of themore rearwardly disposed cross-member 52 form the “C-pillar” structuresof the space frame. Finally, the downwardly and rearwardly extendingportion 28 of each of the longitudinal upward members 20 forms the“D-pillar” structures.

A lower rearward cross-member 80 is hydroformed into a rectangularcross-sectional configuration, and extends between the lower ends 30 ofthe rearward vertical portions of the longitudinal upper member 20. Thelower end portions 30 are cut so as to be provided with a cornered edge82 which is constructed and arranged to engage the upper surface 84 andforwardly facing surface 86 of the rearward cross-member 80. The edges82 are welded to the surfaces 84 and 86 preferably by a mig-weldingoperation.

The vehicle space frame assembly 10 fisher includes a door structure 90,including a hydroformed lower U-shaped tubular member 92, a straighttubular cross-member 94 which is welded adjacent to the ends of thevertical legs 96 of the U-shaped member 92 and an inverted U-shapedhydroformed member 98 having the opposite leg portions thereoftelescopingly received within the tubular ends of the U-shaped member92. These U-shaped members 92 and 98 are hydroformed once again inaccordance with U.S. Ser. No. 60/061,238.

FIG. 2 is a perspective view of a connection between the rearwardcross-member 52 at one corner portion 74 thereof and the associateduppermost straight portion 26 of one of the longitudinal upper members20. As can be appreciated from the partial perspective view of FIG. 4and the cross-sectional view of FIG. 3, which illustrate only thestraight portion 26 of the connection, each of the uppermost straightportions 26 has a recess 100 formed therein. This recess 100 is formedas a result of the hydroforming process. In particular, a net pad isprovided as part of a hydroforming dye assembly so as to give theparticular configuration illustrated. As shown, the recess 100 is formedin an upper wall 101 of straight portion 26. The upper wall 101 formsthe recess 100 with opposite sloping faces 102, and an adjoiningstraight, horizontally disposed wall portion 104. It can be appreciatedthat this particular configuration for the recess is not critical. Forexample, the sloping faces 102 may be more vertically disposed, so as toform a substantially right angle with respect to the surface 104. Asalso can be appreciated from FIGS. 3 and 4, the recess 100 is formedsuch that the bottom wall 110 of the hydroformed straight portion 26 isformed so as to have a corresponding configuration in relation to theupper wall 101. More specifically, the bottom wall portion 110 includesdownwardly and inwardly sloping wall portions 112, which are adjoined bysubstantially horizontally disposed wall portion 114. It should beappreciated, however, that the wall portion 114 has a greater lengththan the wall portion 104. In addition, the sloping wall portions 112preferably slope to a lesser extent than the angle at which the wallportions 102 slope. As a result, the distance between the upper wallportion 101 and the bottom wall portion 110 is substantially less atareas of the recess 100 than immediately surrounding or adjacentportions on opposite sides of the recess. It should be appreciated thatwhile the lower wall 110 formed at the recess 100 generally conforms tothe configuration of the upper wall 101, it is contemplated that thelower wall 10 may be substantially straight as it extends from before,through, and after the areas immediately beneath the recess 100.

Referring back to FIG. 2, the preferred configuration for the uppercross-member 52 is shown, which incorporates a downwardly facing recessat the corner portion 74. While the recess is substantially hidden inFIG. 2, it should be appreciated that it has generally the sameconfiguration as the recesses illustrated in FIGS. 3 and 4 and has ahorizontal or straight surface which rests upon and is fixed to theupwardly facing surface of the wall portion 104 of the uppermoststraight portion 26. At the downwardly facing recess provided incross-member 52, the distance between the wall portions 120, and 122 atthe recessed portion of the cross-structure 52 beneath the cornerportion 74 is substantially less than the distance between such wallportions 120, 122 on opposite sides of the recess.

As a result of the formation of the overlapping recesses formed in thelongitudinal straight portions 26 of the upper members 20 and the cornerportions 74 of the cross-member 52, the overlapping intersectionsforming the connections between the cross-member 52 and laterally spaceduppermost straight portions 26 of the upper members 20 can be made so asto have a reduced cross-sectional profile. It is contemplated that thedesired profile could also be achieved if only one of the overlappingmembers 20 or 52 is provided with a recess, although it is preferred forboth overlapping portions to be provided with such a recess.

A similar overlapping joint connection having recesses is provided atthe connection of the cross-member 50 with the uppermost straightportions 26 of the upper members 20, generally beneath corner portions58 of the cross-member 50. These connections are virtually identical tothe connection illustrated in FIG. 2.

It should also be appreciated that similar recesses are formed in thelongitudinal upper members 20 so as to form connections with oppositeends of the cross-members 44,46, and 48. However, at such connections,recesses formed within the longitudinal upper members 20 are provided inthe upper or outwardly facing wall portion 111 only. The opposing wallportion at these connections is substantially straight, as contemplatedin the discussions above. In addition, the cross members 44, 46, and 48are not provided with any recess, but are simply received withinrecesses at their opposite ends to form reduced profile weldedconnections.

Finally, it should also be appreciated that the same type of connectionis fused to connect the bottom portions 76 of the cross-member 52, whichare received and welded within a hydroformed recesses formed within thelower side rail members 12. Again, in this configuration, only one ofthe wall portions is configured in forming the recess, and the oppositewall portion is substantially flat or continuous with adjoining wallportions, as can be appreciated from area 140 in FIG. 1.

Because the frame structures described above are all hydroformed, aprecisely configured space frame can be achieved. For example, becausethe upper longitudinal structures 19 are hydroformed as a single member20, the desired distance between the forward lower vertical portions 22and the rearward lower vertical portions 30 (i.e., between the “A”pillar structure and “D” pillar structure) can be made within a higherdegree of accuracy and precision in comparison to constructions in whichthe structures are separately formed and then connected. The same istrue in the cross-car direction, e.g., the distance between the “C”pillar structures or between the “B” pillar structures is preciselyachieved in accordance with the accuracy to which the cross members 50and 52 can be hydroformed.

FIG. 5 is a perspective view of a second embodiment of the presentinvention. FIG. 5 illustrates a space frame 200, which incorporates amain body module or vehicle cage 210 and a front structural assemblyprovided by a front end module assembly 400 connected to the front endof the vehicle cage.

The vehicle cage 210 is similar in many respects to the space frame 10of the first embodiment. The vehicle cage 210 comprises a pair oflaterally spaced, longitudinally extending lower side rail structures211. Each of the side rail structures 211 is preferably a hydroformedrail member 212. Each lower side rail member 212 has a relativelystraight forward portion 214 which transitions into an upwardly andrearwardly sloping portion 216. In addition, each of the side railmembers 212 includes a generally straight or slightly arcuate portion218 extending rearwardly from the upper rearward end of the intermediateportion 216. Unlike the first embodiment, however, the side rail membersalso include a downwardly and then rearwardly extending rearward portion219 forming the rearward end of the side rail members 212. The portions216, 218, and 219 provide the rear “kick-up” for accommodating a rearwheel well.

The side rail members 212 are each formed from a straight tubular blank(formed by conventional roll forming and seam welding) which are bentgenerally into the “S” configuration shown, then diametrically expanded,and shaped in any conventional hydroforming operation.

The vehicle cage 210 further includes a pair of upper structures 219.Preferably each structure 219 is a hydroformed longitudinal upper member220. Each of the upper members 220 includes a forwardly disposed, lowervertical portion 222, which transitions into an upwardly and rearwardlyextending forward portion 224. Portions 222 and 224 form the “A-pillar”structures on the left and right sides of the vehicle space frame 200,as generally indicated at 225. Each longitudinal upper member 220further includes an uppermost, longitudinally extending, generallystraight portion 226, which forms a roof structure and which transitionsfrom and extends rearwardly from the upwardly and rearwardly extendingforward portions 224.

Each longitudinal member 220 terminates towards the rearward portion ofthe generally straight portion 226, where it is welded to a rear loop oraperture ring structure 203 of the vehicle cage. The rear aperture ringstructure 203 comprises two U-shaped tubular hydroformed members 229 and231 to form a loop or ring 227. The upper U-shaped member 229 isinverted and is connected at opposite ends thereof to the opposite endsof the upright lower U-shaped member 231 at a glove joint 237. Moreparticularly, opposite legs 243 of the upper U-shaped member 229terminate in a cross sectional diameter portion that is smaller than thecross-sectional diameter of the opposite ends of the opposite legs 241of lower U-shaped member 231. Thus, the end portions of the legs 243 ofthe upper U-shaped member 229 are received within the open ends of thelower U-shaped member 231 and then welded in place. The portions of theupper U-shaped member 229 immediately above the end portions that arereceived within the legs 241 of lower member 231 are diametricallyexpanded so as to form integral flange-like surfaces that engage themating upper edges of the open ends of the upwardly extending legs 241of the lower member 231, so as to limit the extent to which the legs 243of upper member 229 can extend within the legs of lower member 231. Thisrear aperture ring 227 defines a rear opening for a vehicle rear door orlift gate.

The legs 243 of the upper U-shaped member 229 and the legs 241 of thelower U-shaped member 231 cooperate to form laterally spaced, generallyparallel, and vertically extending D-pillar structures 228 of the frameassembly 200. The upper U-shaped member 229 has a laterally extendingbight portion 248 connected between the leg portions 243.

The junctures between the legs 243 and the bight portion 248 are joinedto the rear ends of the generally straight portions 226 by a weldedconnection (“joint E”) as illustrated best in FIGS. 7 and 20-22. Itshould thus be appreciated that each upper longitudinal member 220comprises an entire A-pillar structure and also defines the portion atwhich the upper end of an associated D-pillar structure 228 isconnected. Thus, it can be appreciated that the hydroformed tubularmembers 220 in conjunction with the aperture ring 227 define both alongitudinal dimension and a cross-vehicle dimension of the vehicle cage210. The aperture ring 227 also defines a height of the rearward end ofthe space frame 200.

The aperture ring 227, being formed from two hydroformed U-shapedmembers provides enhanced dynamic stability of the space frame from amatchboxing standpoint, to prevent twisting of the frame in itsapplication environment.

As also shown, the leg portions 241 of the lower U-shaped member 231 areconnected by a bight portion 245. The junctures or transitions betweenthe bight portion 245 and the opposing leg portions 241 are joined at awelded connection with rearward ends of the side rail members 212, asbest illustrated as Joint D in FIGS. 7 and 17-19 (see welds W). As bestshown in FIG. 19, a notch 213 is cut in the end of each side rail 212 tonestingly receive the lower U-shaped member 231.

As shown, each longitudinal upper member 220 preferably has anirregular, almost pyramidal or trapezoidal cross-section. In addition,it should be appreciated that both of the longitudinal upper members 220have been hydroformed from a single tubular blank structure, preferablyformed from two separately roll-formed tubular blanks which have beenbutt-welded to one another at butt-welded connection 232. In particular,as described with the first embodiment, the butt-welded connection 232is performed prior to the hydroforming operation and connects twoseparate tubular blank members of different diameter to one another.

In view of the rather severe bend of 30° at the junction of thegenerally straight portion 226 and the portion 224 that forms theA-pillar structure, the longitudinal upper structures 220 are formedaccording to the teachings of U.S. Ser. No. 60/061,238, filed Oct. 7,1997. This methodology is also preferably used to form the upperU-shaped member 229 and the lower U-shaped member 231, as well as theinverted U-shaped cross members 250 and 252 to be described.

As described with the first embodiment, the lower side rail members 212have a varying cross-sectional configuration along its longitudinalextent. Preferably, the side rail members 212 extend generally from aposition immediately forward of the lower portions 222 of the A-pillarstructures to the rearward end of the main body module or cage 210. Theforward ends of the side rail members 212 are joined to front side railstructures 411 of the front frame assembly 400. In particular, the frontside rail structures 411 are hydroformed side rail members 412 and areglove-fitted into the forward opened ends of side rail members 212 andwelded in place, as is best illustrated as “Joint 0” in FIGS. 10 and 41.

Preferably, in similar fashion to the A-pillar being formed from twotubular members butt-welded at joint 232, the side rail members 212 areformed from two separately roll-formed tubular blanks which have beenbutt-welded to one another at butt-welded connection 247 (see FIG. 6).The butt-welded connection 247 is performed prior to the hydroformingoperation and connects two separate tubular blank members of differentdiameter to one another as discussed above in relation to the A-pillarstructure.

As best illustrated as Joint C in FIGS. 7 and 16, the lower portion 234of each of the lower vertical portions 222 is received in a hole 235 inthe upper wall and a hole 223 in the lower wall of the forward portion214 of each lower side rail member 212. The holes 235 and 223 are formedeither during the hydroforming process in what is known in the art as ahydropiercing operation (see U.S. Pat. No. 5,460,026, herebyincorporated by reference), or cut into such form-fitting configurationafter the hydroforming operation is completed. After the lower portions234 are positioned as shown, they are preferably mig-welded in place atwelds W. As can also be seen in FIGS. 10 and 16, a cross frame member251 forms a cross structure that connects the lower side rail members212 to one another by an L-shaped bracket 253. The bracket 253 connectsthe cross frame member 251 at the same longitudinal location as the Apillar structure lower portion 222, relative to the longitudinaldirection of the side rail member 212. Otherwise stated, the framemember 251 is at least partially overlapping with the lower portion 222relative to the longitudinal direction of the side rails 212.

A plurality of additional cross structures provided by cross framemembers 255, 257, and 259 are also connected between the side railmembers 212. This is best illustrated in FIGS. 6 and 12-15. Inparticular, members 255 and 257 constitute front seat support members.As shown in FIGS. 12 and 13, the opposite ends of the cross member 255is received within a recess 261 in the lower wall 263 of each of theside rail members 212 and welded in place. As shown in FIG. 13, anoptional L-shaped bracket 265 may be welded between the side wall ofside rail member 212 and the upper surface of the cross member 255 foradded rigidity. It should be appreciated that the cross member 257 is ofsimilar structure and purpose as cross member 255, and is secured insimilar fashion between the side rail members 212 (see FIG. 35).

The cross member 259 constitutes a riser-floor pan support structure. Asbest illustrated as Joint B in FIGS. 14 and 15, the cross member 259 isconnected between the side rail members 212 at portions of the side railmembers immediately forwardly of the rear kick-up for accommodating therear wheels. As can be appreciated from the figures, the ends of thecross member 259 are provided with notches 277 that are formed tonestingly receive the underside of the side rails 212. The cross member259 is welded at welds W to the side rails 212.

The vehicle cage 210 is shown in combination with a vehicle front door267 in FIGS. 13, 24, 38. As shown, the door 267 incorporates ahydroformed lower cross member 269, which is welded to a door outerpanel 271. A peripheral rubber seal structure 273 is fixed to the door267 and surrounds the door to form a door seal with the lower rail (oran aesthetic covering therefor) when the door is closed. The lower crossmember 269 forms the lower portion of a door frame structure that issimilar to the door frame structure 90 illustrated in FIG. 1. The sealstructure 273 also forms a seal with the A-pillar structure when thedoor is closed, as illustrated in FIG. 24. Also illustrated in FIG. 24is a portion of a forwardly disposed vertical structure 275 of the door267, which forms the downwardly extending forward leg portion of thedoor structure, similar to the forward portion 75 of the door upperframe structure 98 illustrated in FIG. 1. The structure thus forms partof an inverted, tubular hydroformed structure, similar to the structure98 of FIG. 1.

A plurality of cross-structures are interconnected between thelongitudinal upper members 220. In particular, a first cross-structureis provided by a first cross-member 244. The cross-member 244 comprisesa hydroformed tubular member having a substantially rectangularcross-section and is connected between the longitudinal upper members220, preferably between the lower portion 222 and upwardly andrearwardly extending portion 224 of the A-pillar structure, andimmediately above the butt-welded connections 232. Similarly, a crossstructure provided by a, cross-member 246 connects the two longitudinalupper members 220, generally between the upper ends of the A-pillarstructures (formed by portions 222,224). Preferably, each of thesecross-members 244 and 246 has a closed cross-sectional configuration andis hydroformed from a circular tubular blank in conventional fashion.

The cross-members 244, 246 have opposite ends joined to the upperstructures 220 at joints F and G, respectively. Joint F can be bestappreciated from FIGS. 8 and 23-25, while Joint G can be bestappreciated from FIGS. 8 and 26-28. These joints are formed by weldedconnections. Recesses 233, 238, 239, and 249 are formed in thelongitudinal upper structures 220, preferably using a net pad during thehydroforming operation, as was described with the first embodiment. Theopposite ends of cross member 244 are received in the recesses 239 andare welded in place (see FIG. 23), while the opposite ends of crossmember 246 are received in recesses 249 and welded in place (see FIG.26). Joint G may be facilitated by a structural adhesive connection, asindicated by 247 in FIG. 27, which can be used in lieu of, or inconjunction with welding.

A pair of inverted U-shaped hydroformed cross-structures 251 and 253 aredisposed between the cross-members 246 and the rear aperture ring 227.Specifically a hydroformed forwardly disposed U-shaped cross member 250has a generally horizontally disposed bight portion 254 extending in across-car direction, and a pair of leg portions 256 extending downwardlyfrom the opposite ends of the bight portion 254. Comer portions 258 ofthe cross-member 250 form the transition between the bight portion 254and the respective leg portions 256 (see FIG. 8). The corner portions258 are disposed in overlying or overlapping relation with adjacent,underlying portions of the uppermost straight portions 226 (see Joint Hin FIGS. 29-31). The corner portions are preferably adhered to thestraight portions by a structural adhesive A. FIG. 30 illustrates how avehicle roof R would interface with the cross member 250.

The bottom end portions 260 of the leg portions 256 are received withinopenings in the side rail members 212 and welded in place at welds W(see Joint J in FIGS. 8 and 35).

The rearward cross-structure 253 is provided by a rear cross-member 252.The rear cross-member 252 comprises a bight portion 270, which issubstantially horizontally disposed and extends in the cross-cardirection. The bight portion 252 transitions into vertically downwardlyextending leg portions 272 from the opposite ends of the bight portion270. Corner portions 274 form the transition between the bight portion270 and the respective leg portions 272 (see Joint I in FIGS. 8 and32-34). The corner portions 274 are disposed in overlapping or overlyingrelation to adjacent portions of the uppermost straight portions 226,and are preferably joined by a structural adhesive A.

The corner portions 258 and/or 274 may be disposed in hydroformedrecesses formed in the exterior configuration of the uppermost straightportions 226 as in the first embodiment.

The leg portions 272 have ends 276 thereof received within holes oropenings 277 which are punched in the top and bottom walls of theassociated lower side rails 212 and mig-welded in place at welds W, asbest shown as Joint K in FIGS. 8 and 36.

Again, the teachings of U.S. Ser. No. 60/061,238 are preferably employedto avoid wrinkling at the bends (corner portions 258 and 274) in thecross-members 250 and 252.

It should be appreciated that the legs 256 of cross-structure 250 formthe “B-pillar” structures of the space frame 200. Similarly, the legs272 of the more rearwardly disposed cross-structure 252 form the“C-pillar” structures.

It should be appreciated that at each of the overlapping jointsdiscussed above in the second embodiment, net pads can be used in thehydroforming die for forming recesses in the hydroformed tubes tofacilitate joining of the parts, as can be appreciated from thediscussions of the first embodiment, particularly with respect to FIGS.2-4. It should be appreciated that this type of connection can be at anyjoint, and not only at the corners 258 and 274.

Because the frame members described above are all hydroformed, aprecisely configured space frame can be achieved. For example, becausethe upper longitudinal structures 220 are hydroformed and extend fromthe A-pillar structure to an upper connection with the D-pillarstructure, the length of the space frame between the A-pillar andD-pillar structures can be precisely defined. In addition, the rearaperture ring, formed by two hydroformed U-shaped members the, cross-cardimension (between the D-pillar structures) as well as the verticaldimension of the space frame can be precisely defined.

Preferably, as illustrated in FIGS. 39 and 40, the lower end portions260 of the B-pillar structures formed by vertical portions 256, afterbeing received and welded in place in the opening within the lower railmembers 212 (see FIG. 35) are each further supported by a front gussetmember 290 (see FIG. 39) and a rear gusset member 292 (see FIG. 40),which are preferably fixed in place by a structural adhesive. Similarly,the A-pillar structures are each provided with a rear gusset 294 (seeFIGS. 37 and 38) for supporting the connection between each A-pillarstructure and the associated lower rail.

The front end module 400 is preferably made from a plurality ofhydroformed members, including lower front frame rail members 412connected with the side rail members 212 as best illustrated in FIG. 41that provide laterally spaced, rigid elongated structures on each sideof the front module 400. As shown, the rear ends of front frame railmembers 412 are telescopingly received in the front ends of the siderail members 212.

In addition, a pair of upper longitudinally extending structures areprovided by elongated members 420. The elongated members 420 arepreferably hydroformed and define the upper front end of the vehicle(e.g., for supporting body panels including the front hood). As shownbest in FIG. 42, each member 420 is provided with a recess 422 formed inthe opposite ends thereof for receiving the A-pillar structure of thespace frame, and is then welded in place. Because the members 420 areconnected with the A-pillar structures, the A-pillar structures willabsorb longitudinal force applied to the members 420. Similarly,longitudinal forces applied to the front rail members 412 will beabsorbed by the rail members 212. As a result, the front end module 400allows front end forces to be absorbed and countered by the vehicle cage210.

FIGS. 11 and 43 illustrate the manner in which a rear quarter panel Qwould be mounted on the space frame 200. Preferably, the rear quarterpanel would be fixed to the C-pillar structure 272 (Joint R) and to therearward portion of the longitudinally extending portion 226 by astructural adhesive A, as best seen in FIG. 45.

As best seen in FIG. 44, a vehicle roof R can be mounted to thelongitudinally extending portion 226 by a bracket B. The bracket B mayalso support a corner panel P. A front driver's side door D is alsoillustrated in FIG. 44, the parts of which can be appreciated from themore detailed description of a rear passenger door 374.

Joint R, which is the interface between the vehicle C-pillar structureand the rear passenger door 374, and the connection of the C-pillarstructure 272 with the rear quarter panel Q is illustrated in FIG. 45.Preferably, the door 374 has a peripheral hydroformed door frame 376manufactured by hydroforming two U-shaped tubular members in accordancewith the teachings above in relation to the door in the firstembodiment. The frame 376 is welded to outer door sheet metal 377. Adoor seal 378 and door window 379 are also shown.

FIGS. 46 and 47 are enlarged cross-sectional views of Joints S and T ofFIG. 11, respectively.

FIG. 48 is a cross sectional view of a hydroforming die assembly forillustrating the method of the present invention. Of course, the shapeof the die cavity in accordance with the present invention isparticularly adapted to the shape of the new and advantageous tubularparts now contemplated. FIG. 48 is representative in nature andillustrates two hydroforming ram assemblies 500 and 502, which haveouter ram members, respectively, which are movable to engage and sealopposite ends of a tubular blank 510, which has been bent (for examplein a CNC bending machine) to fit within a die cavity 512 of ahydroforming die structure 514. The blank 510, which is in the form of atubular metallic wall, can represent any U-shaped or inverted U-shapedmetallic wall or blank member discussed above. The tube 510 ispreferably immersed in a water bath so as to be filled with hydroformingfluid. The rams 500 and 502 include hydraulic intensifiers, which canintensify the hydroforming fluid to expand the tubular wall or blankinto irregularly outwardly deformed conformity with the die surfaces soas to fix the tubular wall or blank into a predetermined irregularexterior surface configuration as disclosed in U.S. Ser. No. 60/061,238.The outer rams 504 and 506 push inwardly into the die structure so ascreate metal flow within the blank 510 so as to replenish or maintainthe wall thickness of final tube part within about +/−10% of theoriginal wall thickness of the blank (i.e., to compensate for wallthinning during diametric expansion of the tube). As discussed above,greater detail of the method is disclosed in the incorporated U.S. Ser.No. 60/061,238.

It should be appreciated that the methodology of U.S. Ser. No.60/061,238 would not be used for parts that were not bent at an angle ofless than 30°. Preferably, straight parts, such as cross member 246 maybe hydroformed in accordance with U.S. Ser. No. 08/915,910, filed Aug.21, 1997, entitled Hydroforming Die Assembly For Pinch-Free TubeForming, hereby incorporated by reference.

Briefly, in accordance with the hydroforming methodology of the presentinvention, a first tubular metal blank having a generally U-shapedconfiguration is placed into the hydroforming die assembly, the dieassembly having die surfaces defining a die cavity. The ends of the tubeblank are sealed, and hydraulic fluid is pressurized by an intensifierwithin the interior of the first tubular metal blank so as to expand theblank into conformity with the die surfaces of the die cavity andthereby form a first of the hydroformed upper longitudinal members, suchas longitudinal members 20 of the first embodiment or 220 of the secondembodiment. A second tubular metal blank having a generally U-shapedconfiguration is also placed into a hydroforming die assembly, andpressurized fluid expands this second tubular metal blank so as toexpand the blank into conformity with the die surfaces of the die cavityand thereby form a second of the hydroformed upper longitudinal members(20 or 220). The first and second upper longitudinal members eachprovide at least one pillar of the space frame. For example, each upperlongitudinal member 20 of the first embodiment provides both theA-pillar and the D-pillar structures, while in the second embodiment,each member 220 provides a respective A-pillar structure as an internalpoint thereof. First and second lower side rail members (12 or 212) areprovided, and the at least one pillar structure of the first hydroformedupper longitudinal member is connected to a first of the spaced lowerside rail members. The at least one pillar structure of each secondhydroformed upper longitudinal member (20 or 220) is connected to asecond of the spaced lower side rail members. The first and second lowerside rail members are positioned in laterally spaced relation to oneanother. The first and second lower side rail members (12 or 212) areconnected to one another with laterally extending connecting structure,for example, the cross member 80 of the first embodiment and crossmembers 251, 255, and 257 of the second embodiment.

The present invention also contemplates that the U-shaped cross members(e.g., 50, 52, 250, and 252, are hydroformed by placing a tubular metalblank having a generally U-shaped configuration into a hydroforming dieassembly and then providing pressurized fluid inside the blank to expandthe blank to conform to the die surfaces. The first and second lowerside rail members are positioned in laterally spaced relation to oneanother. A first end of the hydroformed cross member is connected to thefirst lower side rail member, and a second end of the hydroformed crossmember is connected to the second lower side rail member.

It is to be understood that each of the hydroformed tubular membersdiscussed herein is formed from an integral tubular blank from a tubestock. Preferably, the blank is formed by conventional roll forming andsubsequent seam welding technology. The tubular blank is then expandedinto conformity with the surfaces defining the hydroforming die cavity,so as to form the tube with a shape corresponding to the desired shapefor the part. Preferably, the ends of the tubular blank are forcedinwardly toward one another during the hydroforming operation so as toreplenish or maintain the wall thickness of the formed part within apredetermined range of the wall thickness of the initial tubular blank,as discussed in more detail in the aforesaid application U.S. Ser. No.60/061,238. It should thus also be appreciated that each of thehydroformed tubular parts disclosed in the present application is formedfrom a single tubular member which is positioned within the hydroformingdie, although the single tubular blank member may itself be formed byjoining two or more tubular members to one another (e.g., by buttwelding the tubular blank members in end-to-end fashion) before it isplaced in the hydroforming die to be hydroformed. In this sense, eachhydroformed tubular structure disclosed herein is an integrally formedtubular structure, meaning that it has been hydroformed into a singulartubular structure that corresponds to a desired shape, and does notcomprises a plurality of tubular structures fixed to one another. Inaddition, when formed in accordance with the preferred method, each ofthe hydroformed tubular structures in accordance with the presentinvention has only a single longitudinal seam weld, which weld wasperformed in creating the original tubular blank. This is distinct frommore conventional tubular frame members, which comprise two C-shaped orclam-shell halves welded to one another in facing relation along twoseams.

While the invention has been disclosed and described with reference witha limited number of embodiments, it will be apparent that variations andmodifications may be made thereto without departure from the spirit andscope of the invention. Therefore, the following claims are intended tocover all such modifications, variations, and equivalents thereof inaccordance with the principles and advantages noted herein.

What is claimed is:
 1. A method of forming a space frame for a motorvehicle, said method comprising: placing a first tubular metal blankhaving a generally U-shaped configuration into a hydroforming dieassembly having die surfaces defining a die cavity configured to receivesaid first blank therein; providing pressurized fluid to an interior ofsaid first tubular metal blank while disposed within the die cavityconfigured to receive the same so as to expand said blank intoconformity with the die surfaces of said die cavity and thereby form afirst hydroformed upper longitudinal member having a longitudinallyextending portion and a pair of pillar-forming portions extending fromopposite ends thereof; placing a second tubular metal blank having agenerally U-shaped configuration into a hydroforming die assembly havingdie surfaces defining a die cavity configured to receive said secondblank therein; providing pressurized fluid to an interior of said secondtubular metal blank while disposed within the die cavity configured toreceive the same so as to expand said blank into conformity with the diesurfaces of said die cavity and thereby form a second hydroformed upperlongitudinal member having a longitudinally extending portion and a pairof pillar-forming portions extending from opposite ends thereof;providing first and second lower side rail structures and connectingstructures; connecting said first and second hydroformed upperlongitudinal members, said first and second lower side rail structuresand said connecting structures together in fixed relation to form saidspace frame, said connecting procedure with respect to said firsthydroformed upper longitudinal member and said first lower side railstructure comprising connecting the pair of pillar-forming portions ofsaid first hydroformed upper longitudinal member to said first lowerside rail structure in a relationship wherein the pair of pillar-formingportions provide a first A pillar and a first rearward end pillar on thefirst lower side rail structure and the associated longitudinallyextending portion defines a longitudinal length therebetween; and saidconnecting procedure with respect to said second hydroformed upperlongitudinal member and said second lower side rail structure comprisingconnecting the pair of pillar-forming portions of said secondhydroformed upper longitudinal member to said second lower side railstructure in a relationship wherein the pair of pillar-forming portionsprovide a second A pillar and a second rearward end pillar on the secondlower side rail structure and the associated longitudinally extendingportion defines a longitudinal length therebetween.
 2. A methodaccording to claim 1 wherein said first and second blanks are similar insize and shape and wherein the die cavity configured to receive each ofsaid first and second blanks constitutes a single die cavity withinwhich said first and second blanks are separately placed and expanded.3. A method of forming a space frame for a motor vehicle, said methodcomprising: placing a first tubular metal blank having a generallyU-shaped configuration into a hydroforming die assembly having diesurfaces defining a die cavity configured to receive said first blanktherein, said first tubular metal blank being a singular tubular blankstructure; providing pressurized fluid to an interior of said firsttubular metal blank while disposed within the die cavity configured toreceive the same so as to expand said blank into conformity with the diesurfaces of said die cavity and thereby form a first singularhydroformed upper longitudinal member having a longitudinally extendingportion and a pair of pillar-forming portions extending from oppositeends thereof; placing a second tubular metal blank having a generallyU-shaped configuration into a hydroforming die assembly having diesurfaces defining a die cavity configured to receive said second blanktherein, said second tubular metal blank being a singular tubular blankstructure; providing pressurized fluid to an interior of said secondtubular metal blank while disposed within the die cavity configured toreceive the same so as to expand said blank into conformity with the diesurfaces of said die cavity and thereby form a second singularhydroformed upper longitudinal member having a longitudinally extendingportion and a pair of pillar-forming portions extending from oppositeends thereof; providing first and second lower side rail structures andconnecting structures; and connecting said first and second singularhydroformed upper longitudinal members, said first and second lower siderail structures and said connecting structures together in fixedrelation to form said space frame, said connecting procedure withrespect to said first singular hydroformed upper longitudinal member andsaid first lower side rail structure comprising connecting the pair ofpillar-forming portions of said first singular hydroformed upperlongitudinal member to said first lower side rail structure in arelationship wherein the pair of pillar-forming portions provide a firstA pillar and a first rearward end pillar on the first lower side railstructure and the associated longitudinally extending portion defines alongitudinal length therebetween, said connecting procedure with respectto said second singular hydroformed upper longitudinal member and saidsecond lower side rail structure comprising connecting the pair ofpillar-forming portions of said second singular hydroformed upperlongitudinal member to said second lower side rail structure in arelationship wherein the pair of pillar-forming portions provide asecond A pillar and a second rearward end pillar on the second lowerside rail structure and the associated longitudinally extending portiondefines a longitudinal length therebetween, wherein the length of eachof said longitudinal lengths is determined by the corresponding lengthof said die surfaces forming each of said longitudinal lengths.